The invention relates to a mechanical device that indicates pressure or pressure changes in an analog manner. Most desirably, the mechanical device of the invention serves as a barometer, but it can function to sense other types of pressure or pressure changes besides atmospheric pressure.
It has long been the goal of pressure sensors and gauges, particularly barometers, to accurately indicate pressure or pressure changes using the fewest number of and/or least expensive components possible. According to the invention this goal is accomplished, and additional advantages are provided. For example, in the barometer embodiment of the invention, aside from the pressure sensor (e.g. aneroid chamber) and pointer assembly (indicator and spindle or shaft), which are standard components of all barometers, the invention only comprises two basic elements, a cam, and a force transmitting element. In addition to being simple, this allows the barometer to be inexpensive; and the provision of the cam makes it possible to adjust the components to get linear or non-linear readouts, or to transform non-linear movement of a pressure sensing element into accurate arcuate movement of a pointer.
While under some circumstances the assembly of the invention may have one or more gears, typically gears are expensive and therefore are to be avoided. According to various aspects of the invention, an accurate yet simple gearless pressure indicator assembly (such as a barometer) may be provided. Also, the invention can achieve its objectives by using only a single stage of amplification (provided by the cam and lever attached thereto), as opposed to multiple stages in many prior art arrangements (e.g. see U.S. Pat. No. 4,238,958).
According to one aspect of the invention there is provided an analog pressure indicator assembly comprising: A pressure sensitive element having a first portion that moves in a path in response to pressure. A cam having a first curved surface and a second surface, and mounted for rotation about a first axis, and the curved first surface operatively engaging the first portion of the pressure sensitive element. A force transmitting element which is capable of transmitting a force. A shaft mounted for rotation about a second axis. A pointer operatively connected to the shaft. And, the force transmitting element operatively connecting the cam second surface to the shaft in order to cause the shaft to rotate in response to the pressure sensitive element rotating the cam about the first axis.
The terms “operatively connected” or “operative connection” or “operatively connecting” or “operatively connect” or “operative engagement”, or the like, as used in this application mean—as they normally do—any type of link or device [no matter how simple or complex] that allows the components to function as desired.
Where the analog pressure indicator is a barometer, the pressure sensitive element comprises an aneroid chamber (sometimes alternatively called a vacuum chamber, or diaphragm). However, in its broadest aspects, the pressure sensitive element may comprise any conventional or to be hereafter developed mechanical element which senses pressure, or changes in pressure, such as a bourdon tube, rubber or other elastomeric material diaphragm, single or multiple segment bellows, or the like. The path of movement or deflection of the aneroid chamber may be almost precisely linear, or slightly arcuate or non-linear, or complex.
The cam may be made of plastic, or other inexpensive material, wood, metal, composite, or other suitable materials. The first axis about which the cam rotates is preferably substantially perpendicular to the path of movement of the aneroid chamber, and offset from the path of movement in such a way that movement of the aneroid chamber results in rotation of the cam. The cam second surface may comprise a lever arm connected to and extending away from the curved surface, although other configurations may be provided. The curved surface may be shaped to “linearize” the output of the pressure sensitive element. The cam curved surface has portions thereof which are spaced different distances from the first axis, and preferably the curved surface is continuous. The curved surface and lever may provide significant movement amplification (preferably using only a single stage of amplification), that is moving the shaft a greater angular amount than would be expected from a minute movement of the aneroid chamber. The first axis may be provided by a standard pivot pin, shaft stubs, or the like, or by a ball bearing arrangement.
The force transmitting element may be any element which is capable of transmitting a force. Preferably the force transmitting element is operatively connected at or adjacent one end thereof to the lever arm, and at or adjacent the other end to the shaft. The force transmitting element may comprise a bar, a rod, a strand [such as a cable, chain, wire, belt, rope, combination of these elements, or the like], or any other suitable mechanical element. The force transmitting element can be operatively connected to the cam by a pin, or through one or more other intermediate elements. The force transmitting element can also be operatively connected to the shaft by an intermediate element, such as a sprocket (particularly where part of the force transmitting element is a chain capable of engaging a sprocket).
The shaft may comprise a conventional spindle, and the second axis may be substantially perpendicular to (although offset from) the first axis. A conventional pointer is operatively connected to the shaft. The pointer may comprise any conventional or hereafter developed indicator (such as shown in U.S. Pat. Nos. 4,238,958, 4,255,970, 4,361,048, 4,543,824, 4,733,564, or 4,953,404, all incorporated by reference herein). The operative connection between the pointer and the spindle may be a sleeve extending from the pointer and adapted to fit tightly over, or be keyed to, the spindle.
According to another aspect of the invention, there is provided: A gearless barometer comprising: an aneroid chamber having a central portion which moves along a path; a cam having a curved surface which engages the aneroid chamber and which rotates about a first axis at a location spaced from the path; a pointer which rotates about a second axis at all times having the same relationship to the first axis; and an operative connection between the cam and the pointer which transforms rotation of the cam about the first axis to an accurately comparable rotation of the pointer about the second axis without gears. The cam curved surface is preferably biased into operative engagement with the aneroid chamber, as by a torsion spring.
According to another aspect of the invention, there is provided: A gearless pressure indicator assembly consisting essentially of: A pressure sensing element. A cam mounted for rotation about a first axis and having a curved surface engaging the pressure sensing element and a lever arm extending away from the pressure sensing element. A shaft mounted for rotation about a second axis spaced from the first axis, and operatively connected to a pointer. A combination bar/rod and strand operatively connected between the lever arm and shaft to transform pivotal movement of the lever arm into rotation of the shaft. And a biasing element which biases the cam curved surface into operative engagement with the pressure sensing element.
It is the primary object of the present invention to provide a device or assembly which accurately indicates pressure or pressure changes using the fewest number of and/or least expensive components possible. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.